This application claims priority under 35 U.S.C. §119(a) on Patent Application No. 2007-183342 filed in Japan on Jul. 12, 2007, the entire contents of which are herein incorporated by reference.
The present invention relates to a surface-mounted chip-type LED and a method of manufacture thereof, used as a light source in various types of display panels, backlighting for liquid-crystal display devices, and in lighted switches and the like.
Chip-type LEDs have conventionally been used as light sources in various types of display panels, backlighting for liquid-crystal display devices, and in lighted switches and the like.
FIG. 8 illustrates an example of the structure of such a conventional chip-type LED.
This conventional chip-type LED has a dual-layer structure using insulating substrates 81 and 82; a through-hole 83 is formed in the upper insulating substrate 82, and one wiring pattern 84 is formed so as to extend to the inside bottom of the through-hole 83 (in other words, to the upper surface of the lower insulating substrate 81). An LED chip 85 is mounted upon the wiring pattern 84 within the through-hole 83 and is connected to another wiring pattern 86 with a metallic small-gauge wire (e.g. an Au wire or the like) 87. Finally, the surface of the insulating substrate 82 is sealed with a clear resin 88 so that the LED chip 85 and the metallic small-gauge wire 87 are also contained within the clear resin 88.
Because the LED chip 85 is mounted within the through-hole 83, a chip-type LED constructed in such a manner achieves a slim size. However, such a chip-type LED is problematic in that the inner circumferential surface of the through-hole 83 is formed perpendicular to the bottom surface of that through-hole 83, causing low upward reflective efficiency when the LED chip 85 is lit. Furthermore, two insulating substrates, or the substrates 81 and 82, are required, and moreover, because the LED chip 85 is mounted upon the lower insulating substrate 82, the insulating substrate 82 is required to have a certain minimum thickness of an amount that allows the LED chip 85 to be mounted thereupon. This results in problems that it is difficult to achieve a slim size, and the cost of the chip-type LED increases as well.
Chip-type LEDs that attempt to solve these problems have accordingly been provided (for example, see JP H7-235696A).
As shown in FIG. 9, this chip-type LED is structured as follows. A metal sheet 105, which forms one wiring pattern 109, is attached to the back side 1101 of an insulating substrate 110, in which a through-hole 112 is formed, and an LED chip 101 is mounted upon the metal sheet 105 within the through-hole 112 (in other words, upon the wiring pattern 109). The LED chip 101 is connected, using a metallic small-gauge wire 102, to another wiring pattern 104 that is formed on the front surface 1102 of the insulating substrate 110, which is then sealed with a clear resin 111.
With such a structure, the LED chip 101 is mounted directly onto the metal sheet 105, eliminating the need for the second substrate used in the conventional chip-type LED, and the thickness of the chip-type LED can be reduced by that amount as a result.
However, the chip-type LED of the abovementioned JP H7-235696A, connects the LED chip 101 to the other wiring pattern 104 that is formed on the front surface 1102 of the insulating substrate 110 using the metallic small-gauge wire 102. In other words, the position at which the metallic small-gauge wire 102 is connected to the other wiring pattern 104 is high, meaning that the height at which the metallic small-gauge wire 102 is disposed cannot be lowered significantly. This leads to a problem in that the degree to which the thickness of the chip-type LED can be reduced is limited to that height. There is a further problem in that it is necessary to form the other wiring pattern 104 across the external surface of the insulating substrate 110 and to the bottom surface of the substrate, which complicates the manufacturing process.